Joint Estimation of Channel and Preamble Sequence for Orthogonal Frequency Division Multiplexing Systems

1. A system, comprising: an estimation module configured to receive a signal having N sub-carriers, and generate N first estimates for channel gains of the N sub-carriers, where N is an integer greater than 1; a processing module configured to generate N second estimates based on the N first estimates; and a control module configured to generate N differences between each of the N first estimates and corresponding ones of the N second estimates, and estimate (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.

2. The system of claim 1 , wherein the estimation module generates the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.

3. The system of claim 1 , wherein the processing module generates each of the N second estimates by generating weighted averages of the N first estimates.

4. The system of claim 1 , wherein the processing module generates each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.

5. The system of claim 2 , wherein the estimation module generates i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.

6. The system of claim 5 , wherein the processing module generates i sets of the N second estimates based on the i sets of the N first estimates.

7. The system of claim 6 , wherein the control module generates i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.

8. The system of claim 7 , wherein the control module determines a value of i that generates a smallest of the i sums, estimates the preamble sequence present in the signal based on the value of i, and estimates the channel gain based on one of the N second estimates that generates the smallest of the i sums.

9. The system of claim 1 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).

10. The system of claim 9 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.

11. The system of claim 10 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.

12. The system of claim 10 , wherein each of the i preamble sequences is different from others of the i preamble sequences, the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold, and the i preamble sequences are stored in the estimation or the control modules.

13. The system of claim 12 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.

14. The system of claim 1 , wherein the control module identifies a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.

15. A physical layer module (PHY) comprising: the system of claim 1 ; and a transceiver module configured to communicate with the estimation module and receive the signal.

16. A network device comprising: the PHY of claim 15 ; and at least one antenna configured to communicate with the transceiver module.

17. A method for a physical layer (PHY) of a mobile station for estimating channel gain and preamble sequence, the method comprising: receiving a signal having N sub-carriers at the PHY of the mobile station, where N is an integer greater than 1; generating N first estimates for channel gains of the N sub-carriers; generating N second estimates based on the N first estimates; generating N differences between each of the N first estimates and corresponding ones of the N second estimates; and estimating in the PHY (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.

18. The method of claim 17 , further comprising generating the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.

19. The method of claim 17 , further comprising generating each of the N second estimates by generating weighted averages of the N first estimates.

20. The method of claim 17 , further comprising generating each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.

21. The method of claim 18 , further comprising generating i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.

22. The method of claim 21 , further comprising generating i sets of the N second estimates based on the i sets of the N first estimates.

23. The method of claim 22 , further comprising generating i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.

24. The method of claim 23 , further comprising determining a value of i that generates a smallest of the i sums, estimating the preamble sequence present in the signal based on the value of i, and estimating the channel gain based on one of the N second estimates that generates the smallest of the i sums.

25. The method of claim 17 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).

26. The method of claim 25 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.

27. The method of claim 26 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.

28. The method of claim 26 , further comprising storing the i preamble sequences, wherein each of the i preamble sequences is different from others of the i preamble sequences, and wherein the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold.

29. The method of claim 28 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.

30. The method of claim 17 , further comprising identifying a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.

31. The method of claim 17 , further comprising communicating with a transceiver module in a physical layer module (PHY) and receiving the signal from the transceiver module.

32. The method of claim 31 , further comprising communicating with at least one antenna of a network device comprising the PHY and receiving the signal via the at least one antenna.

33. A system, comprising: estimation means for receiving a signal having N sub-carriers and generating N first estimates for channel gains of the N sub-carriers, where N is an integer greater than 1; processing means for generating N second estimates based on the N first estimates; and control means for generating N differences between each of the N first estimates and corresponding ones of the N second estimates, and estimating (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.

34. The system of claim 33 , wherein the estimation means generates the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.

35. The system of claim 33 , wherein the processing means generates each of the N second estimates by generating weighted averages of the N first estimates.

36. The system of claim 33 , wherein the processing means generates each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.

37. The system of claim 34 , wherein the estimation means generates i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.

38. The system of claim 37 , wherein the processing means generates i sets of the N second estimates based on the i sets of the N first estimates.

39. The system of claim 38 , wherein the control means generates i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.

40. The system of claim 39 , wherein the control means determines a value of i that generates a smallest of the i sums, estimates the preamble sequence present in the signal based on the value of i, and estimates the channel gain based on one of the N second estimates that generates the smallest of the i sums.

41. The system of claim 33 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).

42. The system of claim 41 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.

43. The system of claim 42 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.

44. The system of claim 42 , wherein each of the i preamble sequences is different from others of the i preamble sequences, the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold, and the i preamble sequences are stored in the estimation or the control means.

45. The system of claim 44 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.

46. The system of claim 33 , wherein the control means identifies a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.

47. A physical layer module (PHY) comprising: the system of claim 33 ; and transceiver means for communicating with a medium, wherein the transceiver means communicates with the estimation means and receives the signal.

48. A network device comprising: the PHY of claim 47 ; and antenna means for receiving signals, wherein the antenna means communicates with the transceiver means.